Valve opening arrangement and method

ABSTRACT

A valve opening arrangement includes a first contact surface on a first member, and a second contact surface on a second member discrete from the first member. A first and a second opening are provided, and a first and a second valve movable to open and close the first and second opening, respectively, are provided. A yoke is arranged to move the first valve and not the second valve when contacted by the first contact surface and is arranged to move the first valve and the second valve when contacted by the second contact surface.

BACKGROUND AND SUMMARY

The present invention relates generally to a valve opening arrangementand method and, more particularly, to a valve opening arrangement andmethod including a yoke for moving one or both of two valves.

In many engines today, each cylinder is provided with two intake and twoexhaust valves. The valves are often opened by a yoke connected to thetwo intake or exhaust valves. The yoke is generally forced in onedirection to open the valves by a rocker arm and, usually, springs urgethe valves to a closed position after the rocker arm force is released.The architecture of many engines places the valve yoke in closeproximity to the rocker arm pivot shaft. This creates packaging issuesthat prevent the use of state of the art single-valve engine brakeactuation. It is desirable to actuate only the valve closest to therocker shaft to better utilize rocker arm mechanical advantage and allowhigher cylinder pressures for more braking power. While this might beaccomplished with a hydraulic lash adjuster that actuates through thevalve yoke on the inboard valve, the proximity of the yoke to the rockershaft on group engines does not leave any space to include this piston.Thus, the lash adjustment must be made to the entire yoke so that bothvalves are actuated under braking. This requires lower pressures for thegiven valve train package.

It is desirable to provide a valve opening arrangement that can providefor flexible valve actuation arrangements while occupying minimal space.It is also desirable to provide such a valve opening arrangement thatfacilitates both single valve actuation during engine braking and twovalve actuation during engine exhaust.

In accordance with an aspect of the present invention, a valve openingarrangement comprises a first contact surface on a first member, asecond contact surface on a second member discrete from the firstmember, a first and a second opening, a first and a second valve movableto open and close the first and second opening, respectively, and a yokearranged to move the first valve and not the second valve when contactedby the first contact surface and arranged to move the first valve andthe second valve when contacted by the second contact surface.

In accordance with another aspect of the present invention, a method ofactuating exhaust valves in an engine is provided. The engine comprisesat least one cylinder, the cylinder comprising first and second exhaustvalves. In the method, a first contact surface on a first member ismoved to a first valve open position in which the first contact surfacecontacts a yoke and thereby moves the first valve and not the secondvalve to an open position. A second contact surface on a second memberis moved to a second valve open position in which the second contactsurface contacts the yoke and thereby moves the first valve and thesecond valve to the open position, the first and second members beingdiscrete from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention are well understoodby reading the following detailed description in conjunction with thedrawings in which like numerals indicate similar elements and in which:

FIG. 1 is a schematic, partially cross-sectional view of a valve openingarrangement according to an embodiment of the present invention in aneutral position;

FIG. 2 is a schematic, partially cross-sectional view of a valve openingarrangement according to an embodiment of the present invention in afirst open position;

FIG. 3 is a schematic, partially cross-sectional view of a valve openingarrangement according to an embodiment of the present invention in asecond open position; and

FIG. 4 is a schematic, top view of a valve opening arrangement accordingto an embodiment of the present invention; and

FIG. 5 is a schematic view of a valve opening arrangement according toan embodiment of the present invention.

DETAILED DESCRIPTION

A valve opening arrangement 21 according to an embodiment of the presentinvention is shown in FIGS. 1-3. The valve opening arrangement 21comprises a first movable contact surface 23 which, in the illustratedembodiment, is part of a first member, here first rocker arm 25, and asecond movable contact surface 27 which, in the illustrated embodiment,is part of a second member, here a second rocker arm 29. The first andsecond members will ordinarily be discrete from each other. The firstand second movable contact surfaces 23 and 27 do not have to be part ofrocker arms 25 and 29. They may, for example, form part of reciprocatingmembers such as pistons. An aspect of the present invention includes useof a valve opening arrangement in connection with an engine 41 includingone or more cylinders 43, however, the invention is not limited to suchuses.

The valve opening arrangement 21 also comprises a first and a secondopening 31 and 33, and a first and a second valve 35 and 37 movable toopen and close the first and second opening, respectively. A yoke 39 isarranged to move the first valve 35 and not the second valve 37 whencontacted by the first movable contact surface 23 as seen in FIG. 2, andis arranged to move the first valve and the second valve when contactedby the second movable contact surface 27 as seen in FIG. 3. The yoke 39can be arranged to move the first valve 35 and/or the second valve 37 bycontacting them directly or, more typically, via contact with first andsecond valve stems 45 and 47 associated with the first and second valves35 and 37, respectively. In an embodiment of the present inventioninvolving an engine 41, the first and second openings 31 and 33 andfirst and second valves 35 and 37 are exhaust valves for a cylinder 43.The yoke 39 is arranged to move the first valve 35 to an open positionwhen the yoke is contacted by the first movable contact surface 23 andis arranged to move the first valve 35 and the second valve 37 to openpositions when contacted by the second movable contact surface 27.

Ordinarily, the yoke 39 will be pivotable, i.e., the yoke is notconstrained to only vertical movement as is typically the case where acenter pin is provided. As seen in FIG. 1, the first and second valves35 and 37 will ordinarily be spring loaded to a closed position relativeto the first and second openings 31 and 33. While the first and secondvalves 35 and 37 can be urged to a closed position by any suitablemeans, typically springs 49 will be mounted around the first and secondvalve stems 45 and 47 and contact, at a bottom of the springs, a surface51 above the cylinder 43 and, at a top of the springs, flanges 45 f and47 f extending from the first and second valve stems. Thus, when thevalve stems 45 and 47 are moved by the yoke 39, the flanges 45 f and 47f compress the springs 49 against the surface 51 above the cylinder 43so that the first and second valves 35 and 37 are moved from the firstand second openings 31 and 33 into the cylinder 43.

The yoke 39 can contact the top ends of the valve stems 45 and 47. Atleast the second valve stem 47 will ordinarily have a rounded top 53that will be received in a correspondingly rounded recess 55 in thebottom surface 57 of the yoke 39. The first valve stem 45 willordinarily have a less rounded top 59 that will contact the bottomsurface 57 of the yoke 39. The top 57 of the first valve stem 45 willordinarily have some radius or chamfer to facilitate rocking and slidingrelative to the yoke 39. A skirt 61 can descend from the yoke 39 on thesides of the tops 53 and 57 and can function together with the roundedtop 53 and rounded recess 55 in the second valve stem 47 and the yoke tokeep the yoke oriented relative to the valve stems.

When the first movable contact surface 23 contacts the yoke 39, it willordinarily be arranged to contact the yoke at a first contact point 63proximate the first valve stem 45 so that, as seen in FIG. 2, the yokewill pivot around the rounded top 53 of the second valve stem 47 androunded recess 55 in the yoke, i.e., it defines a pivot point orfulcrum. By contacting the yoke 39 at the first contact point 63, thefirst movable contact surface 23 will apply force primarily to thesprings 49 keeping the first valve 35 in the closed position and, thus,will only move the first valve. The second valve 37 will ordinarily notbe moved when the first movable contact surface 23 contacts the firstcontact point 63. When the second movable contact surface 27 contactsthe yoke 39 as seen in FIG. 3, it will ordinarily be arranged to contactthe yoke, usually at a center contact point 65 proximate a center of theyoke, in such a manner that the yoke does not pivot and the springs 49associated with both the first valve 35 and the second valve 37 will becompressed to open both valves substantially simultaneously.

The first and second rocker arms 25 and 29 are ordinarily pivotablymounted on a common shaft 67. A centerline C67 of the shaft 67 to acenterline C69 of pushrods or rollers 69 that contact cams 71 and 73 ona camshaft 75 for moving the valves 35 and 37, respectively, isordinarily the same distance D1 for the first rocker arm 25 and thesecond rocker arm 29. A distance D2 between the first movable contactsurface 23 and the shaft 67 is ordinarily less than the distance D3between the second movable contact surface 27 and the shaft, i.e., thefirst movable contact surface is “inboard” of the second movable contactsurface, and the rocker ratio D3/D1 is greater than the rocker ratioD2/D1. This arrangement minimizes the force required to be transmittedfrom the camshaft through the first rocker arm 25 to open the firstvalve 35 when the first movable contact surface 23 contacts the yoke 39.This arrangement can reduce potentially harmful forces on the camshaftduring an engine braking operation as the first rocker arm 25 willordinarily be pivoted to open the first valve 35 only during the enginebraking operation when forces required to open the valves are generallysubstantially higher than during normal exhaust operation when thesecond movable contact surface 27 contacts the yoke.

As seen in FIG. 4, the first rocker arm 25 and the second rocker arm 29can be configured to facilitate contacting first and center contactpoints 63 and 65 on a yoke 39 that is substantially aligned along alongitudinal axis of the first rocker arm. It will, however, beappreciated that other configurations to permit contact with the firstand center contact points on the yoke can be provided, such as byorienting the yoke perpendicular to longitudinal axes of first andsecond rocker arms. In FIG. 4, it will be seen that the first rocker arm25 extends in a substantially straight line, when viewed from above,from the shaft 67 on which it is pivotably mounted to the first movablecontact surface 23 so that the first movable contact surface ispositioned proximate the first contact point 63. An arm 29 a of thesecond rocker arm 29 can curve or bend around a forward end of the firstrocker arm 25 so that the second movable contact surface 27 ispositioned proximate the center contact point 65 on the yoke 39. Thesecond rocker arm 29 can include a second portion 29 b that extends overpart of the first rocker arm 25 and includes an opening through whichthe shaft 67 can extend. The second portion 29 b can provide additionalstability.

The camshaft 75 will ordinarily be arranged to cause the first rockerarm 25 and the second rocker arm 29 to pivot at different times, e.g.,the camshaft will cause the first rocker arm to pivot when the secondrocker arm is not pivoted and/or the first rocker arm will pivot at adifferent frequency than the second rocker arm.

The first movable contact surface 23 can be part of a piston 77 movablydisposed in a cylinder 79 provided in the first rocker arm 25. Thepiston 77 may be controlled to extend to one or more active positions inwhich the first movable contact surface 23 can contact the first contactpoint 63 on the yoke 39 when the first rocker arm 25 is pivoted forward,and to retract to an inactive position in which the first movablecontact surface cannot contact the first contact point on the yoke, evenif the first rocker arm is pivoted forward. The position of the piston77 can be controlled in a variety of ways.

As seen in FIG. 5, the piston 77 can be driven to an active position byhydraulic pressure in the cylinder 79 provided through a line 81 leadingto a suitable source 83 of hydraulic fluid and a pump 85, however, theycan be moved by any suitable means, such as by being moved mechanically,pneumatically, or via electrically operated or magnetic means. Whenhydraulic pressure is relieved or reduced, the piston 77 can be moved toan inactive or retracted position by any suitable means, such as by aspring, such as the spring 49 loading the valve 35 transmitting force tomove the piston through the yoke 39. U.S. Pat. No. 5,193,497, U.S. Pat.No. 5,609,133 and U.S. Patent Application Publication No. 2004/0112330disclose embodiments of rocker arms with extendable pistons, includingfluid lines and valves not illustrated here, and are incorporated byreference. The position of the piston 77 can be controlled by, forexample, a controller 87 that is provided to send appropriate signals toone or more of a valve 89 in the line 81 and the pump 85 to cause fluidto be pumped to the cylinder 79 to move the first movable contactsurface 23 on the piston 77 to an active position. The controller 87 cansend such signals when, for example, a signal is received by thecontroller to perform an engine braking operation. The signal may besent to the controller 87 from, e.g., a sensor 91 that senses acondition calling for engine braking.

In addition to facilitating engine braking, selective opening andclosing of the exhaust valve or valves 35 and/or 37 can facilitateperforming functions such as raising the exhaust gas temperature in anengine. Copending International Patent Application No. PCT/US06/61908,filed on the same date as the present application, entitled, VALVEOPENING ARRANGEMENT AND METHOD, naming Mack Trucks, Inc., as applicant,and naming Edward Smith, Chun Tai, and Timothy Suder, as inventors,discloses, e.g., increasing engine exhaust temperature by selectiveopening and closing of an exhaust valve of a cylinder and isincorporated by reference. According to an aspect of the presentinvention, the piston 77 is moved outward so the first movable contactsurface opens the first valve 35 to achieve desired engine exhausttemperatures.

A method of actuating first and second exhaust valves 35 and 37 in anengine 41 involves an engine comprising at least one cylinder 43, thecylinder 43 comprising the first and second exhaust valves. In themethod, as seen in FIG. 2, a first contact surface 23 is moved from aneutral position (FIG. 1) to a first valve open position in which thefirst contact surface contacts a pivotable yoke 39 and thereby moves thefirst valve 35 and not the second valve 37 to an open position. Thefirst contact surface 23 can be disposed on a first rocker arm 25 thatis pivoted by a cam 71 on a camshaft 75.

As the camshaft 75 continues to rotate, another cam 73 can contact asecond rocker arm 29 on which a second contact surface 27 can bedisposed, thereby moving the second contact surface to a second valveopen position (FIG. 3) in which the second contact surface contacts thepivotable yoke 39 and thereby moves both the first valve 35 and thesecond valve 37 to the open position. The cams 71 and 73 can be arrangedso that the first rocker arm 25 and the second rocker arm 29 pivot atdifferent times and/or different frequencies.

When the first contact surface 23 contacts the pivotable yoke 39, thepivotable yoke can pivot about a pivot point that can be defined by arounded top 53 of a valve stem 47 for the second valve 37 that isreceived in a rounded recess 55 in the bottom surface 57 of thepivotable yoke 39. When the second contact surface 27 contacts thepivotable yoke 39, the pivotable yoke will ordinarily not pivot aboutthat pivot point.

The first contact surface 23 can also be part of a piston 77 andmovement of the first contact surface to the first valve open positioncan comprise moving the piston relative to a cylinder 79 in which thepiston is movably disposed. The cylinder 79 can be formed in the firstrocker arm 25 and can be moved from a retracted, inactive position, toone or more extended active positions in which it can be moved bypivoting the first rocker arm to contact the pivotable yoke 39. Thepiston 77 can be extended, for example, when it is desired to perform anengine braking operation and retracted when it is desired to ceaseengine braking. For example, the first rocker arm 25 can pivot underaction of the cam 71 and the pivoting action of the first rocker arm maynot result in the first contact surface 23 contacting the pivotable yoke39 until the piston 77 is extended to an active position. By contrast,the regular pivoting of the second rocker arm 29 under action of the cam73 can always cause the second contact surface 27 to contact thepivotable yoke to move the valves 35 and 37 substantially simultaneouslyto, for example, permit exhaust to escape from the cylinder 43.

In the present application, the use of terms such as “including” isopen-ended and is intended to have the same meaning as terms such as“comprising” and not preclude the presence of other structure, material,or acts. Similarly, though the use of terms such as “can” or “may” isintended to be open-ended and to reflect that structure, material, oracts are not necessary, the failure to use such terms is not intended toreflect that structure, material, or acts are essential. To the extentthat structure, material, or acts are presently considered to beessential, they are identified as such.

While this invention has been illustrated and described in accordancewith a preferred embodiment, it is recognized that variations andchanges may be made therein without departing from the invention as setforth in the claims.

1. A valve opening arrangement, comprising: a first contact surface on afirst member; a second contact surface on a second member discrete fromthe first member; a first and a second opening; a first and a secondvalve movable to open and close the first and second opening,respectively; and a yoke arranged to move the first valve and not thesecond valve when contacted by the first contact surface and arranged tomove the first valve and the second valve when contacted by the secondcontact surface, wherein the first and second members are first andsecond rocker arms.
 2. The valve opening arrangement as set forth inclaim 1, wherein the yoke is arranged to move the first valve to an openposition when contacted by the first contact surface and arranged tomove the first valve and the second valve to open positions whencontacted by the second contact surface.
 3. The valve openingarrangement as set forth in claim 2, wherein the yoke is pivotable. 4.The valve opening arrangement as set forth in claim 3, wherein the firstcontact surface is arranged to contact the yoke proximate a first end ofthe yoke.
 5. The valve opening arrangement as set forth in claim 4,wherein the second contact surface is arranged to contact the yokeproximate a center of the yoke.
 6. The valve opening arrangement as setforth in claim 3, wherein the second contact surface is arranged tocontact the yoke proximate a center of the yoke.
 7. The valve openingarrangement as set forth in claim 3, wherein the yoke contacts first andsecond valve stems associated with the first and second valves,respectively, at least one of the first and second valve stems having anend defining a pivot point of the yoke.
 8. The valve opening arrangementas set forth in claim 1, wherein the yoke is pivotable.
 9. The valveopening arrangement as set forth in claim 8, wherein the first contactsurface is arranged to contact the yoke proximate a first end of theyoke.
 10. The valve opening arrangement as set forth in claim 9, whereinthe second contact surface is arranged to contact the yoke proximate acenter of the yoke.
 11. The valve opening arrangement as set forth inclaim 8, wherein the second contact surface is arranged to contact theyoke proximate a center of the yoke.
 12. The valve opening arrangementas set forth in claim 8, wherein the yoke contacts first and secondvalve stems associated with the first and second valves, respectively,at least one of the first and second valve stems having a rounded enddefining a pivot point of the yoke.
 13. The valve opening arrangement asset forth in claim 1, wherein the first and second rocker arms arepivotably mounted on a common shaft and the first contact surface isdisposed closer to the shaft than the second contact surface.
 14. Thevalve opening arrangement as set forth in claim 1, wherein thearrangement comprises a camshaft arranged to cause the first rocker armand the second rocker arm to pivot at different times.
 15. The valveopening arrangement as set forth in claim 14, wherein the camshaftcauses the first rocker arm to pivot when the second rocker arm is notpivoted.
 16. The valve opening arrangement as set forth in claim 1,wherein the first contact surface is part of a piston movably disposedin a cylinder in the first rocker arm.
 17. An engine comprising thevalve opening arrangement of claim
 1. 18. A method of actuating exhaustvalves in an engine, the engine comprising at least one cylinder, thecylinder comprising first and second exhaust valves, comprising: movinga first contact surface on a first member to a first valve open positionin which the first contact surface contacts a yoke and thereby moves thefirst valve and not the second valve to an open position; and moving asecond contact surface on a second member to a second valve openposition in which the second contact surface contacts the yoke andthereby moves the first valve and the second valve to the open position,the first and second members being discrete from each other, wherein thefirst and second members are first and second rocker arms.
 19. Themethod of actuating exhaust valves in an engine as set forth in claim18, wherein, when the first contact surface contacts the yoke, the yokepivots about a pivot point.
 20. The method of actuating exhaust valvesin an engine as set forth in claim 19, wherein, when the second contactsurface contacts the yoke, the yoke does not pivot about the pivotpoint.
 21. The method of actuating exhaust valves in an engine as setforth in claim 18, wherein the first contact surface is part of a pistonand movement of the first contact surface to the first valve openposition comprises moving the piston relative to a cylinder in which thepiston is movably disposed.
 22. The method of actuating exhaust valvesin an engine as set forth in claim 18, wherein the first and secondmembers are first and second rocker arms pivotably mounted on a commonshaft, the method comprising pivoting the first and second rocker armsat different times.
 23. The method of actuating exhaust valves in anengine as set forth in claim 18, wherein the first and second rockerarms are pivotably mounted on a common shaft and the first contactsurface is disposed closer to the shaft than the second contact surface.24. The method of actuating exhaust valves in an engine as set forth inclaim 18, comprising moving the first valve and not the second valve toan open position during an engine braking operation and moving the firstvalve and the second valve to the open position during an exhaustoperation.